Open 3D Human Anatomy

Foot

3D Printed Skeletal Right Foot. Printed using freely available 3D files from the BodyParts3D project

There isn’t much that is “open” in the proprietary world of medical device design and development. Designs are guarded, competition is spirited, employees and vendors are bound by strict non-disclosure agreements. Yet for all the varied and confidential pursuits that we undertake in this industry, we all have at least one interest in common: human anatomy. Everything we design travels through, or is placed within, some part of the human machine. A machine so ubiquitous that while I am using one at this very moment, most of you are as well at this same moment. And yet despite eons of medical study and inquiry, collaboration, and publication, it holds its secrets in plain view. The blueprints for this most essential of machine are  strangely out of reach.

Sources of 3D Models

We can freely download 70,000 technical drawings and 3D CAD models for nuts, bolts, and mechanical components from McMaster Carr [mcmaster.com], but they don’t sell body parts, so no luck there. There are great sources for viewing 3D anatomy, like ZygoteBody.com. But if you want to download native 3D files, you’re going to have to pay. 3DScience.com sells medically accurate models for animators, illustrators, and engineers. They cost hundreds or thousands of dollars, and they’re probably worth it. The good folks at Pacific Research Laboratories [sawbones.com] can sell you dimensionally accurate polymer based models for product testing or demonstrations, as well as 3D CAD files representing them. These things are great, but they are neither open nor free.

Modern medical imaging, including CT and MRI scanners, provides a wealth of 3D data, but it isn’t easily translated into a form that is useful for engineering. Commercial software like Mimics [materialise.com] does a nice job of this, again for a price. OsiriX is an awesome open-source program for viewing medical datasets, and with considerable effort, it is possible to extract 3D structures in a format that can be used for engineering (example described in an older post, but I really should write a new post some day with details on how to create such models). OsiriX hosts a number of example DICOM data sets [osirix-viewer.com], which are treasure troves of freely accessible digital human anatomy, for anyone ambitious enough to try to extract it.

Visible Human and BodyParts3D

I recently discovered the NIH/NLM Visible Human Project®, which is a public effort to develop “complete, anatomically detailed, three-dimensional representations of the normal male and female human bodies”. (The ® seems suspicious for an NIH project, doesn’t it?) The project and related initiatives, underway since 1989, have produced many gigabytes of  data, and I’m sure have entertained countless scores of grad students and post-grads. But unless I’m missing something, I can’t find any publicly available 3D solid or surface files derived from these impressive data sets. Refusing to be deterred though, I Googled obsessively until I hit paydirt, in an unexpected place: The Journal of Nucleic Acids Research.

In the 2008 paper BodyParts3D: 3D structure database for anatomical concepts, (abstract on PubMed, open access PDF from oxfordjournals.org) some ambitious researchers in Japan set out to create:

BodyParts3D, a dictionary-type database for anatomy in which anatomical concepts are represented by 3D structure data that specify corresponding segments of a 3D whole-body model for an adult human male

The project was funded by The Integrated Database Project, Ministry of Education, Culture, Sports, Science and Technology of Japan. (Arigatō!) The website alone is quite impressive, and is even translated into English (see http://lifesciencedb.jp/bp3d/?lng=en). But this project goes beyond just displaying pretty pictures… The native 3D models for thousands of carefully rendered body parts are made freely available under a Creative Commons Share-Alike license! And they can be downloaded from an FTP site, in high resolution!

Finally, a complete source of 3D digital human anatomy that is freely available, accessible, and suitable for use in with solid and surface CAD software. From Japan! The files are available in Wavefront OBJ format [wikipedia.org], which can be imported as a 3D surface into CAD software like SolidWorks, finite element analysis (FEA) software like Abaqus or Ansys. These files can also be manipulated in open-source programs like Blender [blender.org] or Meshlab [meshlab.org]. Either of these can also easily convert the .OBJ files into .STL files that can be printed on a 3D printer! Like a kid in a candy shop, I’ve created a few of these already, and hope that others will create more. Here’s the basic procedure that I used.

Creating STL models from BodyParts3D

  1. Download and unzip the OBJ files. The originals are at ftp://ftp.biosciencedbc.jp/archive/bodyparts3d/, but I’ve made a copy (as permitted by the CC-SA license) in case the originals disappear, and to avoid taxing their FTP server in case this gets popular (which I hope it does!). You can grab my copy of the 547MB zip file here: BodyParts3D_3.0_obj_95.zip [docs.google.com].
  2. Find the FMA number of the body part of interest. You can do this using the web interface at http://lifesciencedb.jp/bp3d/?lng=en or by searching the English version of the the parts list (parts_list_e.txt inside the zip file). It helps to know something about anatomy, of course. It also helps to know that many of the FMA numbers on the list refer to groups, rather than individual parts.  For example, FMA9664 “foot” contains FMA70664 “set of toes”, which contains FMA25047 “big toe”, but  you will find none of them in the list of .OBJ files. Instead, you need to find FMA230986 “middle phalanx of right little toe” and 27 other bones if you’re trying to build a complete skeletal model of the right foot.
  3. Create a new empty project in Meshlab, and import one or more .OBJ file of interest. Each .OBJ will be on a separate layer in the project, and Meshlab doesn’t make it easy to figure out how to work with layers. Hint: Filters > Layer and Attribute Management.
  4. Save the Meshlab project at this time if you think you might want to do some more work later.
  5. Merge all visible layers into one. Filters > Layer and Attribute Management > Flatten Visible Layers.
  6. Save the mesh as an STL file. File > Export Mesh > select .STL as type.
  7. Close the project without saving to preserve the layer organization for each component.

Slicing STL files

Many organic models like these are difficult to print on an Ultimaker, MakerBot, or similar 3D printer because there are no flat surfaces to build up from. So its often helpful to slice the model in half, or slice the bottom off a model. For this, I use Netfabb for Ultimaker, a commercial application that I bought with my printer. Netfabb also makes a basic version of their application available for free, and I think it will also work for slicing and repairing STL files. It is available here: http://www.netfabb.com/basic.php. My procedure:
  1. Create a new empty project in Netfabb
  2. Import the .STL file from above. Part > Add
  3. Rotate the part into a desirable orientation, so “up” is in the direction of the +Z axis. Part > Rotate
  4. Move the Z cutting plane to the desired location using the “Cuts” slider at the right. Click “Execute Cut”, then “Cut”
  5. In the parts window at the upper right, delete the part of the cut to throw away.
  6. Right click on the cut part to keep, and choose Export part > To .STL
  7. If offered the opportunity to repair the geometry, do so!
  8. Prepare for printing using your tool of choice. I’m partial to Cura [github.com], which I use for everything.
  9. Print, and/or…
  10. Upload to Thingiverse, and tag with “bodyparts3d”

Challenge

This data set is not perfect. It is derived from a single donor, and with 2mm resolution, much of the detail was subject to artistic interpretation. These models were never intended to be  anatomically perfect, but they are an excellent free and accessible resource for artists, engineers, makers, and bio-hackers. I have converted several into models suitable for printing, and you can do the same! Here are the first ones that I put up on Thingiverse:

The conclusion of this effort is inevitable… So who will be the first to reconstruct a complete 3D printed assembly of our immortal Japanese donor? The challenge is now declared! Leave a comment here when its done…

One Year of Electric Driving

I’ve driven my Chevy Volt for over a year now, and the numbers are in, with help from voltstats.net:

  • 12,376 total miles driven
  • 9,956 battery powered electric miles (80%)
  • 2,420 gasoline generator powered miles (20%)
  • 68 gallons of gasoline
The majority of my driving is a 34 mile round trip, easily less than my fully charged range, which varies between 35 and 42 miles. About a third of the gasoline powered miles can be attributed to long distance road trips to Pinnacles (200 miles) or Los Angeles (750 miles), and the rest are day trips around the Bay Area. I’m happy to report that the Volt has been solid and reliable. It’s fun to drive in the future!

Electricity bill doubled

The number one question that people ask me about owning a Volt: “So how much has your electric bill increased?”. The answer is “its complicated”. The cost of electricity varies with usage, varies with the season, and with EV specific time-of-use rate plan that I switched to when I bought the car,  it also varies with the time of day, and day of the week. So the true costs of electricity need to be evaluated on the basis of a full year. Comparing a full 12 months of electricity costs before owning an EV with the same 12 months after buying an EV, the final score: $801/year before the Volt, and $1,564/year with the Volt. So that’s an increase of  $762, roughly doubling my electric bill.

Electric consumption increased 50%

So if my electric bill doubled, does that mean that my electricity consumption doubled with the car? Far from it. Home charging the car for a year added about 2,800 kWh, or about 233 kWh per month. That’s about a 50% increase over normal household consumption.

Household consumption is consistent and below average

Are my electric rates skewed because of high household electricity consumption (from air conditioning, or other variable demands)? No. The average annual electricity consumption in California was 6,296 kilowatt‐hours (kWh) per household in 2010, according to the 2009 California Residential Appliance Study conducted for the California Energy Commission. The chart below shows my household consumption, excluding EV charging, for 12 months before and after buying the Volt. This makes it clear that my normal household electricity usage is far from excessive, and in fact is less than average. Excluding EV charging consumption from this year, annual electric consumption is virtually identical to last year.

PG&E Rates are Crazy

PG&E’s “EA9 XB Residential Time-of-Use Service for Low Emission Vehicle Customers” provides baseline off-peak rates less than $0.05/kWh, and the Volt knows to only charge itself when the off-peak rates are in effect. So the 2,800 kWh of EV charging electricity should cost 2,800 x $0.05 = $140, right? Wrong! Instead, adding 50% to total electricity demand roughly doubles the total cost. This all happens through the combined magic of tiered rates and time-of-use rates. Tiers are typical in California electricity rate plans, including the conventional E1 residential rate plan that I used last year. With a tiered system, rates increase as usage increases, so this hits particularly hard for EV households. In the summer, I commonly reach the punitive >201% of baseline tier, with rates that can range up to 10 times the baseline. The E9A rate plan, an option specifically designed for EV households, adds another twist: rates change with the season and the time of day. So while off-peak rates can be under $0.05/kWh, they surge to $0.30/kWh or above $0.54/kWh in the summer during peak times. So the cheap electricity at night is more than offset by very expensive electricity for air conditioning on hot summer days. A typical summer electricity bill from PG&E looks like this:

Excerpt from a PG&E electric bill

My effective electric rate increased by 22%, and is 50% higher than the national average

So what are the true effective rates? Well, in the twelve months prior to owning an EV, my average rate under the standard E1 residential rate plan was $0.14/kWh. In the following twelve months, under the E9A time-of-use rate plan, my average rate increased to $0.18/kWh. From the chart below, its clear that in the winter months, the E9A plan offers effective rates that are equal to or lower than last year’s $0.14/kWh. In the summer months, though, rates are substantially higher. The EPA energy costs on the window sticker of a Volt assume the national average of $0.12/kWh, so the $0.18/kWh effective rate in PG&E’s California is 50% higher than the national average. It would be higher still if my household demand were higher than average, or if (gasp!) I owned a second EV.

Volt saves $1,180 in energy costs, compared with the car it replaced

So what’s the bottom line? How do the energy costs for a Volt compare with the gasoline costs of a conventional car? Well, that depends on the car used for comparison. My previous car required premium gas (as does the Volt) and averaged 24 mpg during the years that I drove it. Using California monthly average premium gasoline prices from the California Energy Commission, gas for my old car would have cost $2,167 for the 12,100 miles I drove in the past 12 months. That’s $18/100-miles. For the Volt, during this period, I used $293 in gas, and the incremental cost of electricity (compared with the previous year) was $767. So that’s a total of $1,059 in energy costs for the Volt, or a annual savings of $1,108. At $9/100-miles, that’s almost exactly half the energy costs for a 24 mpg conventional car.

EV energy costs vary by season

The chart above is strange. The slope of the Volt cost curve flattens out from 2,500 miles to 7,500 miles, which happens to correspond to the winter months. With E9A rate plan, the Volt energy advantage is much more impressive in winter, when a Volt operates for about 1/3 the cost of a conventional car. In the summer, the advantage is less impressive, with energy costs reaching 2/3 the costs of gasoline at times.

 What next?

With a year of data in the bag, I can get a better understanding of the costs and benefits of a solar system. This introduces yet another time-of-use rate plan option, as I described in Decoding Time of Use Rate Plans. And to make things even more interesting, PG&E plans to retire the crazy E9A rate plan, and replace it with a different crazy EV-A rate plan. The new plan was originally proposed in September 2011, and met with dozens of protests, including one from me. PG&E responded with a somewhat less objectionable proposal, which appears to have won support of the CPUC. Jack Lucero Fleck has followed these matters closely, and has a written a nice summary of the current PG&E proposal, and a letter to the CPUC with additional analysis.

We’re at the dawn of an electrified revolution that will have a profound impact on auto manufacturers, electric utilities, and the fossil fuel industry. Prospective EV buyers, and current EV owners face a shifting landscape, and considerable uncertainty about the true costs of energy. Governments and regulated utilities will stumble forward toward the inevitable future. It will be an interesting journey. I’ve been in the future for a year now, and complicated as it may be, I’m not going back!

The full year data and source charts from this post can be viewed in greater detail as a Google Spreadsheet. Comments, criticisms, and suggestions are welcome!

Open Source Human Anatomy

3D Printing Aortic Bifurcation

3D Printed Aortic Bifurcation

I first saw a MakerBot Thing-O-Matic in action at the 2011 Bay Area Maker Faire, and it was truly a thing of beauty. I’ve used rapid prototyping machines and services since the mid 90′s, but here was something that you could build yourself, and have on your own desk! Wow. Later in the year, I happened to have a free day in New York during the NYC Maker Faire, so I was drawn to revisit this hacker dreamscape. There, I met @ErikDeBruijn, one of the developers of the Ultimaker: an elegant build-it-yourself 3D printing machine capable of relatively high speeds, stunning resolution, and a comparatively large print volume. I became immediately obsessed with visions of 3D printed anatomical structures, and medical device prototypes. I asked Erik if the Ultimaker was being used commercially, and he knew of a few customers that were using it in schools, and at least one other that was offering a service making 3D prints by the hour. Medical device development, not so much. That only made me more interested.

Later that day, I saw a great talk by Bre Pettis (@Bre) of MakerBot fame (30 minute video on Fora.tv). An icon of the open source hardware movement, Bre gave lots of examples of digitized “things” that are freely shared on sites like Thingiverse, where users can upload, download, share, modify, and combine digital objects. And now print them out, too, effectively “teleporting” physical objects among like minded citizens of the internets. Digital “mashups” of Yodas, Gantstas, and Rabbits delighted the maker-faithful in attendance, while evoking dismissive comments from the guy sitting behind me: “What’s the point?” Dismissive guy, and many like him, see a toy. Which it is. But its more than a toy.

A few quotes from Bre’s talk resonated with me:

If you’re not sharing, you’re doing it wrong!

If you’re at a company, and keeping things secret… Stop it!

Publish those things (even if they’re not done, or done done)… Just share them, because so much of the future depends on it.

These are the noble words of an open source evangelist, and the principles upon which Linux, Firefox, Wikipedia, Arduino, and countless other open source projects depend. And then there’s my professional universe of medical device design and development. An industry that relies upon proprietary designs, trade secrets, secure patents, guarded intellectual property. The opposite of open. And yet, everything that we do in my industry is directed at improving the human condition, which is very much in the common interest of all humans. Is there a way to be “open” in a “closed” industry?

It isn’t easy. I wrote about the opportunity and challenges in Open Medsystems a few of years ago.  Medical device development is expensive, and it generally isn’t going to get funded unless the investors have some confidence that they can profit from their investment. So NDA’s will be signed, secrets will be kept, patents will be filed, and knowledge will be sequestered. Brilliant engineers and designers will face the same challenges, each alone in their own respective proprietary silos, not knowing of their kinship, not benefiting from each other’s ideas or mistakes. In the end perhaps one will win, or both will lose.

But there is hope. I’ve tried to do my part by publishing Open Stent Design on NitinolUniversity.com, releasing Stent Calculator on Google Code. But I think there’s a bigger “open source” opportunity for the medical device community, and I’m not alone. 3D medical imaging technologies, like CT scans and MRI’s, have made amazing advances in the last decade. These increasingly ubiquitous machines create torrents of 3D data sets, each a unique atlas of human anatomy, and each an exquisite three dimensional map of  a diseased system, organ, or tissue. These medical imaging data sets hold secrets waiting to be discovered -they describe the environment in which medical devices must do their healing work. 3D imaging data, usually in DICOM format, is easily anonymized, and easily rendered and manipulated with open source software such as the excellent OsiriX [osirix-viewer.com]. Translating medical imaging data sets into useful 3D geometry for analysis or simulation is messy work (see segmentation [Wikipedia]). But it is important, and at least one group is working on developing a Cardiovascular and Pulmonary Model Repository [VascularModel.org] to do just that. Sponsored by NIH, this effort will collect medical imaging data sets for several body systems, perform segmentation, and make the raw data and analysis available to the public.

Freely available 3D anatomical data + open source 3D printers = freely available (plastic) body parts! Rapid prototyping of proprietary 3D data is nothing new in the medical device development world… but 3D printing of freely available anatomical models derived from freely available anonymized medical imaging data is all kinds of awesome! 3D printed blood vessels, organs, and bones can be used to mold or cast realistic benchtop models, which can be used to test and challenge medical device concepts in a realistic environment… Or better yet, many realistic environments, reflecting the many individual humans they are designed to help. And that is some true open-source mojo at work in a closed industry, to be benefit of all.

So after honing my Ultimaker skillz on snakes, whistles, cars, and alien eggs (“What’s the point?”), I have turned my attention to the beloved OsiriX DICOM Sample Library [osirix-viewer.com], and tackled the aortic bifurcation of the AMNESIX model. After some quality time with OsiriX, I had a rough export of the aorta and iliac bifurcation, which I then cleaned up in MeshLab [meshlab.org], sliced using Netfabb [netfabb.com], then printed using ReplicatorG [replicat.org]. And though it isn’t final, done, or done done, it is now shared as Thing:15942 on Thingiverse!

 

Proposed change to PG&E E9 Time-of-Use Plan

I’ve had the Volt for about a month now, and my electron-fueled travels have been perfectly fantastic. As of this afternoon, I have driven 1,002.7 miles and consumed 1.1 gallons of gas. Still, I can not yet answer the question that I get most often: “What about your electric bill?”

At the beginning of the month, I changed my service plan from the standard issue PG&E E1 residential rate plan to E-9A, a “time-of-use” plan designed for customers who charge electric vehicles at home. With this plan, rates are higher during peak times, and lower at off-peak times, thus providing a good incentive to charge up the car at night when demand on the grid is low, and there is plenty of generation capacity with electrons to spare. Complicated as this is, the Volt allows me to program in all of the rate details, and it figures out when to charge itself.

Until this month, I was able to use PG&E’s website to download daily and hourly demand history from my SmartMeter. Now that I’ve switched to a plan where this hourly usage data actually matters, it is no longer available. Thanks PG&E! So I will not know the true costs for this plan until I get the first bill in a few weeks.

Just the other day, a forum post at gm-volt.com caught my eye: Major change in PG&E CA E9 TOU rates. It seems that PG&E proposed some “helpful” changes to the E9 plan on September 26, 2011. In Advice Letter 3910-E, they propose a new rate schedule. According to this letter, the changes will cause an overall increase in payments for 3/4 of the customers on the E9A plan. Since I had gone to the considerable trouble of Decoding TOU Rate Plans not long ago, I decided that it was time to dust off my spreadsheet and calculate the impact of the proposed change for my expected usage.

The perplexing result of this effort confirmed the same surprising conclusions of some other PG&E EV customers: the new E9 plan is substantially worse than the old E9 plan, and is actually the same or better than the standard E1 plan. The results of one year of simulated use is depicted in the figure below.

Comparing current and proposed E9 time-of-use rates with the standard E1 plan. If my situation is typical, these "helpful" proposed changes will render E9 useless, drive customers to stay on E1, and eliminate any incentive for EV owners to charge at off-peak times.

PG&E’s proposed change makes the E9 plan useless: EV owner will have no reason to choose a time-of-use plan, and will have no economic incentive to charge at off-peak times. This change seems to be completely counter to the public interest, and to PG&E’s own best interest. Go figure.

Here’s a link to my spreadsheet for calculating simulated annual billing under various confusing and convoluted rate plans. I think it’s reasonably accurate, but who knows. If you find it useful, or can make any improvements, please drop a comment here.

TOU_Simulator.xlsx

UPDATE (10/9/11) The Numbers Are In!

The first PG&E bill has been posted, and it is quite a whopper! Electric costs are $219 for 896 kWh compared with $122 for 683 kWh in the same period last year: An increased cost of 80%, for 31% more electrons. That’s the magic of tiered rate plans: the more you use, the higher the incremental cost. As it turns out, this billing period is historically the highest of the year for us, and this year, there were more hot days than usual – so lots of A/C during expensive peak hours. I estimate that the car should account for no more than 7 kWh/day on average, but our total usage was nearly 8.5 kWh/day higher this year. Unfortunately, it is nearly impossible to unravel the cost impact for the extra A/C from that for the Volt. So rolling everything together, in the first month, the cost of additional electricity (plus 1.1 gallons of gas) works out to 11.64 cents/mile, or a modest 31% savings relative to my old 24 MPG car. I’ll update the stats monthly, or until I get bored. Here’s a link to my Google Spreadsheet:

Volt Dollars per Mile

 

Decoding Time of Use Rate Plans

My roof, without solar panels

While I’m waiting for the new Volt to arrive, I’ve been researching the economics of a residential solar system. By “researching,” I actually mean geeking-out on all the technical details, and attempting to unravel and reconstruct the engineering and economics of the systems that I’m considering. There have been many discoveries along the way, some of which are explained in excruciating detail here for two reasons: 1) because Google couldn’t provide me the answers that I was seeking, and 2) I probably need some better hobbies.

Introduction

My home in Pleasanton bakes in the California sun, and has an unobstructed southern facing roof that if perfectly situated for photovoltaic panels. Our electricity demand has been about 6,000 kWh per year, which isn’t too high for a house of our size in Pleasanton. The car will add about 2,400 kWh to that, and with the standard tiered rate plan, electricity costs escalate considerably with additional usage. Our friendly local utility, PG&E, is here to help. They have a lots of information on their website http://www.pge.com/electricvehicles/, including a spreadsheet to predict the economics of switching from a standard tiered rate plan (E-1) to a plug-in electric vehicle (PEV) plan with variable rates depending on time-of-use (E-9A or E-9B). Separately, they also have lots of information on solar installations, including a different time-of-use rate plan (E-6) designed to benefit residential solar customers.

Both the E-6 and  E-9 rate plans are eligible for “net-metering”, which means that the electric meter runs in both directions: the utility pays me when I generate more than I use, I pay them when the opposite is true, and we settle up on an annual basis. Since these are time-of-use (TOU) rate plans, the rate is higher during peak times (like summer afternoons), and lower during low demand times (like nights). So I sell electrons to the grid at high rates on sunny days, and buy them back for cheap at night when I charge the car. Perfect!

Methods

Since the convergence of solar and electric vehicles is a fairly new thing, nobody seems to know whether E-6 or E-9 is most beneficial for a customer that has both solar panels and an electric car. So I set out to find the answer, using the most complicated means possible. Here’s the procedure:

  1. Download 52 weeks of hourly SmartMeter data from PGE’s website. This gives me the hour-by-hour electricity demand for my own house in the course of one full year. Unfortunately, this required 52 separate downloads. Thanks, PG&E. Import into Excel, and reformat into 8,760 rows, one for each hour in the year. Add the anticipated demand from charging the Volt on a Level 2 charger: 6 kWh per hour, for two hours, starting at midnight, every weeknight.
  2. For each of the 8,760 data points, figure out which of five different rates apply for each hour, based on the month and time of day. Repeat this for E-6 and E-9 plans.
  3. Now figure out the output from my hypothetical solar system for each of those 8,760 hours. This depends on lots of things: the panel specs, number of panels, inverter, roof orientation, weather, and so on… While this may seem completely intractable, the US Government has developed an application that does all that and more. The National Renewable Energy Laboratory (NREL) has developed a software tool called System Advisor Model (SAM) that simulates the performance of systems under a wide range of conditions. I fed SAM the 8,760 data points that describe my annual usage, and it gave me back the hourly net kWh to or from the grid. Way cool.
  4. With the net energy flow pasted into the spreadsheet, I could now simulate a full year of operating a solar array and a plug-in electric car, both under the E-6 rate plan and the E-9 rate plan.

Results

The system that I modeled consisted of 22 panels, each rated at 235W, for a total rated output of 5.17kW. For my installation, this will provide about 7,800 kWh of energy during a year, and with the car I’ll need about 9,000 kWh.  So I’ll take about 1,200 kWh more off the grid than I’ll send onto the grid. The chart below shows cumulative demand and generation throughout one full year.

The E-6 rate plan has several different rates depending on the time of day and season. The next chart shows net energy to and from the grid during the year for each of the rate categories: summer peak, summer partial-peak, summer off-peak, winter partial-peak, and winter off-peak.

Though I’m 1,200 kWh in debt by the end of year, the picture in dollars is quite different. The power that I generate during the summer peak and summer partial peak periods (the top two lines) is much pricier than the power that I have to buy during the winter periods. So with the E-6 rate plan, I finish this simulated year owing PG&E exactly $18.19.

The E-9A rate plan is similar to E-6, but the rates are more leveraged. The peak rates last for more hours during the day and evening, and the off-peak rates (though lower) last for a shorter period of time. I wanted to figure out if the higher peak rates and long peak hours would be a net benefit with solar generation. The E-9 chart shows what happens: the summer partial-peak period is very profitable, but the costs during the winter off-peak period completely offset the benefits. At the end of the year, I owe PG&E a total of $64.41.

Conclusion

For my circumstances, the E-6 plan is a better option than the E-9 plan, to the tune of about $40. Now you know. Your results may vary.

Resources

There are lots of great resources freely available online that are very helpful for obsessed engineers that are interested in finding ways to spend some of their free time.

  • PGE_TOU_Compare.xls (docs.google.com) is a version of the spreadsheet that I used to calculate all of this stuff. Unfortunately, it was too large to work natively as a Google Spreadsheet, so it has to be downloaded old-skool style.
  • NREL (nrel.gov) developed the System Advisor Model software, which was good for many hours of simulated enjoyment.
  • Open Energy Information (openei.org) provides crowd-sourced data on rate plans for utilities across the country. I found the data there for the E-1 plan that I currently use, updated the data for E-6, and added the data for E-9. The SAM application also interfaces directly with this database.
  • The OpenPV Project (openpv.nrel.gov) was also developed by NREL. It is a comprehensive database of solar installations across the country. It has detailed data on the location, size, and installed cost of PV installations across the country. Compare the statistics from your quotes with those for other systems installed in your neighborhood.
  • As I’ve been planning my system, I’ve been fortunate to work with three very reputable solar installers: Real Goods, SunWize, and REC. If I had three houses, I would buy one from each.

Buying a 2012 Chevy Volt

Silver 2012 Volt

I’ve owned mostly German and Japanese cars, so when we traded in the Subaru Legacy for a 2010 Chevy Equinox last year, it was quite a leap of faith. A Government Motors vehicle in my garage? Strange but true. We have been impressed with just about everything – utility, handling, comfort, reliability, styling. And had we not been so impressed with the ‘Nox, I don’t think I would have remotely considered such a radical new GM offering such as the Chevrolet Volt.

My current ride is a 128i, which is the minimum recommended dose of Ultimate Driving Machine that money can buy. It is an altogether great car. Fun to drive, reliable, sporty, comfortable. It is one of the most fuel efficient cars that BMW makes, but even so, I get a real world average 24 MPG driving to and from work, during commute traffic, with a grandfatherly absence of sportiness. On weekends, it sits in the garage, and we use the Equinox. The coupe format makes it difficult to get the little man in and out when I’m on pickup or dropoff duty. So the car is optimized for a degree of sportiness over efficiency that just doesn’t suit my usage.

My first opportunity to check out the Volt was at Maker Faire in May. It definitely looked bad-ass, and seemed to be everything I was hoping for. Comparable in size to my 128i, four doors, with a fit and finish that seemed even better than the already excellent Equinox. Not long after, I got in touch with Tony at Courtesy Chevrolet in San Jose. When we were shopping for the Equinox, we found Tony after being thoroughly disappointed with the sales experience at the closer Dublin Chevrolet. He gave us a great deal, and made it easy as could be. Turns out that Tony is Mr. Volt at Courtesy, and gave me the scoop on everything I wanted to know.

We took a test drive, and the deal was sealed before I drove off the lot. Clearly, the Volt is an exotic novelty of automotive technology, but 1) it drives and handles just like a normal car, and 2) if it was possible to drive an iPad, this is what it would be like. It is a remarkable combination of ordinary and transformational.  Just like an iPad connects to the same Internet as the desktop PC in my office, the Volt drives on the same roads and delivers the same functionality as an ordinary car. But the experience of driving a Volt for the first time, similar to using an iPad, is like stepping through a portal into the future. In this alternate future, some things are left behind and missed: a real keyboard, a real back seat. The shortcomings, however, are easily eclipsed by the experience offered by this new platform.

EPA Estimated Energy Costs

For my normal commute, the all-electric range of the car will get me to work and back without having to use any gasoline at all, or recharging, which is quite remarkable. I expect that I’ll gladly burn some petrol for the comforts of heat and air conditioning. Maybe I’ll be able to plug in at work and avoid the need for gas altogether. Beyond the convenience and energy efficiency, the Volt also offers an impressive array of wizardry, connectivity, and creature comforts the likes of which I haven’t seen anywhere outside of an Apple Store. So there was no doubt that I wanted to own this car.

The true cost of a Volt is not easy to discern. The sticker price for a well equipped Volt is in the range of $43,700, which certainly seems like quite a premium relative to other small cars. But that is offset by a federal tax rebate of $7,500, and possibly state incentives as well. Fuel (energy) costs are a big factor, too. I figure that the cost of electricity and gasoline for the Volt will be at least half of what it is for my 128i, with the savings greater as the cost per gallon inevitably increases. Then there’s resale value, which is a complete mystery for a new creature like the Volt. The folks at Edmunds.com have a total cost of ownership calculator which attempts to factor in all of these things, including maintenance, fuel costs, and all the rest for a five year period. Here’s a breakdown of what they call the “true cost to own” for several cars that I might compare with the Volt.

5-Year Total Cost of Ownership (edmunds.com)

The Courtesy Difference

This is where we need to take a brief detour to discuss the practice of Market Price Adjustments, also affectionately known as Price Gouging. There are some interesting discussions about this at gm-volt.com, along with lots of other great information. The supply of Volts is limited and demand is high, so some dealerships have elected to avail themselves of the benefits of such market economics. Particularly in Silicon Valley, there are plenty of folks that can afford to pay whatever the dealer asks, so in some sense its hard to fault the dealer for taking their money. As of June 2011, Courtesy Chevrolet has chosen this path. By doing so, they actually have Volts available on the lot for folks that are willing to pay $5,000 or more over MSRP. I’m in no rush to buy a Volt immediately, and Courtesy wasn’t willing to sell one at MSRP, nor order one with a commitment to sell it at MSRP. Certainly they have a right to opportunistically sell Volts above sticker, but they will not sell one to me. Dealers engaging in such practices will likely suffer long term damage to their reputation and credibility for doing so. They have offended the sensibility of early-adopters and influencers, and we have a good memory.

On the other hand, there are also dealers that have elected to sell Volts at GM’s recommended sticker price. Dealers owned by AutoNation are in this category, as are others I’m sure. I recall that when my brother was in the market for a new Corvette C5, the same “opportunistic” pricing practices were prevalent, and Kerbeck Chevrolet in Atlantic City was one of the few that took the high road and gave him a fair deal. I’ve read that they are doing the same with Volts, so Kerbeck deserves the great reputation they have earned. Fortunately, I didn’t have to look as far as the East Coast for such a reputable dealer.

I contacted Fremont Chevrolet, which is about five minutes away from my office. I quickly got a call back from Kurt Mietz, their fleet sales guy, and also Volt specialist. They sell all their Volts at MSRP, so for now you have to order one and wait. It just so happens that Kurt was spec’ing out the first eight 2012 Volts allotted to Fremont, so he asked me how I wanted mine configured. I told him on the phone, and then when I stopped by later that day, he handed me the piece of paper with a tracking number. Done. Absolutely couldn’t have been easier. If you’re in Northern California and shopping for a Volt, give Kurt a ring at (510) 445-8700.

Some other things that I’ve learned… I had wanted the “Cyber Gray” color, but learned that it is not available for 2012 because the supply of the pigment was impacted by the tsunami in Japan. So I went for Silver. We expect that my Volt will be in production sometime in August, rail transportation will take about 30 days, and after that delivery will be sometime around October. Plenty of time to get a 220V charging system installed in the garage. I’ll post Part 2 once the Volt makes it home.

On Sheds

California homes are usually storage challenged. Basements generally don’t exist here, and attics are typically useless. Garages are most often outfitted as man-caves or warehouses. But I’ve noticed that my garage is actually attached to the driveway, and is a convenient place to store our cars when they are not being driven around. So for as long as I’ve lived in this house, the lawnmower, edger, rakes, shovels, and their kin have been trashily resting in a heap on the side of the house. This year, I finally broke down, and decided to buy a shed.

Shed Decision Tree

I found that there are three types of sheds in the universe: Expensive, Cheap, and Very Cheap. It should be noted that all three of these are actually expensive, just to varying degrees. In my case, I was in the market for something about 8 feet by 8 feet in size. So to elaborate… Expensive style sheds are fabricated from actual wood, and assembled like actual buildings, but smaller. Cheap Sheds are, as best as I can tell, pre-fabricated from high-fructose wood-flavored particle fibers, packaged into transportable bundles, and then assembled on site. Very Cheap sheds are fabricated from simulated plastic, and assembled like simulated garbage cans, but larger and more rectangular.

So, considering my personal circumstances, I quickly decided that I was in the market for a Cheap shed. Naturally, I then visited both purveyors of such outdoor storage solutions: orange and blue. Home Depot has aligned itself with an outfit called Tuff Shed. You can specify and buy your Cheap Shed from Home Depot or from Tuff Shed directly. The results are exactly the same in either case. Expensive. The “Garden Ranch” 8×8 shed with shingles and some shelves quoted out at $1,600, delivered and assembled. Seems steep. Over at Lowes, you can buy a Heartland Liberty 8×8 shed for $749 plus shipping, unassembled. Sounds better, but what about my shelves? And assembly? And what if I want a window and weather vane on top? Their website was much less versatile than the Home Depot / Tuff Shed site, so I decided to go to the source. But it didn’t exist.

“Heartland”, it seems, is just a thinly disguised rebranding of the pre-fab sheds sold by “Backyard Buildings & More” aka Backyard Products LLC, which seems to be located somewhere in Michigan. Or, more conveniently, on the interweb at http://backyardbuildings.com. So I dialed them up, found that the Lowes “Heartland Liberty” is suspiciously identical to their “Value Line Seneca” shed, and it can be customized as desired (just the shelves in my case), equipped with shingles, shipped, and assembled for about $1,000. Now that’s the Cheap Shed I was looking for.

I placed the order online, and forgot about it for a week. When I noticed that a shed failed to materialized anywhere in the vicinity of my home or back yard, I became a bit concerned. Checking the email confirmation, they should have called me to schedule delivery within 48 hours. Uh oh. So I called the distributor at the number listed on the invoice, and talked with someone who seemed a bit confused. Eventually, he admitted to finding my order, and asked when I wanted it. Well, how about Monday? No problem. They’ll call in the morning.

On Monday, I got a call from the driver, who wanted to confirm my street address, which he correctly identified. Except he thought it was in Sacramento. Which is about an hour and a half away. Remarkably, though, he and his able assistant actually arrived at the correct location eventually, sporting their “Lowes” shirts. While they seemed a bit put off about having to drive to Pleasanton, they did successfully assemble the thing in about four hours.

Backyard Buildings seemed a bit shady to me when I was considering what to buy, but all and all, everything worked out OK. I would say that the Tuff Shed model that I checked out at the Orange store seemed to have a bit high build quality, but I think that can be attributed almost entirely to the door latch / handle which was much more substantial on the Tuff Shed. Otherwise, they seems to be built from the same particle fiberboard stuff, and both have that weird smell inside. Backyard Buildings doesn’t offer an option for painting, which was available for $131 from Tuff Shed. But I bought some paint for about $30 and did it myself in a couple of hours.

In my research, I found The Internets seemed to be sadly lacking in rambling essays on applied shed research and procurement practices. This unfortunate void has now been filled, as has my freshly painted and still weirdly smelling shed.

Watts Premier: Failure and Redemption

Part I: Failure

An unsuccessful attempt to open the filter.

(If you are interested in a 500 word essay on how not to change the filters on a reverse osmosis filter, please continue. Otherwise, please skip to Redemption below)

In my town, we receive a months supply of free minerals every day, delivered conveniently through the city water supply. This is a wonderful benefit for everyone, especially sinks, faucets, shower doors, spigots, hot water heaters, and all sorts of other plumbing fixtures that automatically accumulate valuable white crystals during their normal use. So rich are these mineral deposits, in fact, that many such fixtures are afforded the opportunity to retire early. Many have.

A few years ago, I decided that we had accumulated more than our fair share of minerals. We installed a water softener, thus magically exchanging our minerals for IONS. Specifically, sodium ions, in fact. And while the toilet, shower, and washing machine are delighted to consume these ions, we didn’t really want to drink them, or cook our spaghetti in them either. So we did some homework, contemplated the options, talked with a plumber. He recommended a Watts Premier WP-5 One Piece Manifold Reverse Osmosis System, conveniently available for delivery from CostCow.com for the low low price of $160. Installed under the sink, it quietly provides us with an infinite supply of drinking water, certified to be free from arsenic, cysts (cryptosporidium, giardia, entamoeba and/or toxoplasm), barium, hexavalent chromium, trivalent chromium, copper, lead, fluoride, cadmium, radium 226/228, selenium, TDS and turbidity. And, of course, sodium ions.

Here’s the problem: the filters need to be changes every six months or so. The first time I attempted this, I gave up, and hired a guy to do it. He was successful, but not without a great deal of frustration, anger, and generous usage of colorful language. Now, having put off this filter changing ritual for, oh about two years, I decided it was time to tackle this thing. Armed with pack of replacement filters, an instruction manual, and a genuine plastic toy wrench that came with the system, I began the simple procedure:

  1. Turn off the incoming water, and drained the pressure from the system, per protocol.
  2. Use genuine plastic toy wrench to unscrew filter bowls. Fail.
  3. Become frustrated, and generously use colorful language.
  4. Consult Watts Premier Troubleshooting page. Fail.
  5. Consult Internets. On the Costco review page, WindWalker from New Jersey suggests “The trick is to unscrew and release some of the tubes first. What happened was that the air pressure pushes against the filter caps tight and makes it hard to budge. But if you loosen us a few tubes (closer to the filter caps), it will release the pressure, and make it much easier to unscrew the filter caps.” Thank you Internets, this is why you were invented!
  6. Remove the tubes and wait a little while, then try again. FAIL. Oh, noes! The Internets have mislead me.
  7. Try harder, adding a pry bar to the genuine plastic toy wrench to get more leverage. Stand on manifold to stabilize filter body, and express increasing rage. FAIL.
  8. Stop for a moment and think about which way loosens the thing, and which way tightens it. Yep, that’s the right way. Enjoy another moment of rage.
  9. Consult the Home Despot. Purchase an $8 Husky Strap Wrench, which looks like just the thing to solve this problem. Remove from packaging. It smells bad.
  10. Apply strap wrench to filter, and attempt to unscrew first bowl. SUCCESS! It starts to move. (ok, good, I was actually unscrewing it in the right direction)
  11. Now repeat with second bowl, apply force, and break new strap wrench in two places. FAIL.
  12. Move the leaky and partially dismembered filter to the garage for a week so it can think about what it has done.
  13. Write to Watts Premier customer service and ask them for advice.
  14. Wait a week, then call them to ask why they haven’t responded.
  15. They haven’t responded because they don’t know what to do either.

Part II: Redemption

Now, for the first time ever, I will reveal to the Internets the successful procedure I have developed for replacing the filters on a Watts Premier WP-5 Reverse Osmosis system:

  1. Remove the entire filter assembly.
  2. Place the whole thing in a tub of hot water. This, people of the Internet, it is secret you came to this page to find.
  3. Drive to the Home Despot and exchange and/or buy an $8 Husky Strap Wrench. Open package. It smells bad.
  4. Remove the filter from the now somewhat less hot water.
  5. Use strap to unscrew the filter bowls.
  6. Celebrate victory.

Part III: Footnote

I was able to contact an actual human at Watts Premier when I called them. Let’s call her Ginger, which I think is her telephone name. She was very apologetic, and very nice, but had no useful advice whatsoever. She did suggest, though, that if I was able get the thing open, I could remove the lower O-ring when replacing the filter bowl, because they’ve found that it can make the seal too tight. O RLY? Well, that’s good to know. Since my hot water + strap wrench trick seems to work OK, I left the second O-rings in there. Wouldn’t want it to be too easy next time!

TCT Theater

Spooky Nitinol Magic

Spooky Nitinol Magic

Every fall for the past dozen years, Washington DC has hosted the annual celebration of cardiovascular medical device innovation, inspiration, teaching, marketing, controversy,  and edutainment known as TCT. During this week, leading physicians, industry brass, deal makers, and investors mix at scientific sessions, banquet rooms, expo halls, bars, and restaurants at the heart of the heart business. Every year, it seems, has at least a few memorably controversial moments.

My first TCT was not in Washington, but in Milano, Italia. The year was 1997, and I was at the cath lab of legendary innovator Antonio Colombo, along with a host of other industry folks, all hoping that this diminutive giant of interventionl cardiology would honor us by using our particular widget during a live case transmission. Alas, the unremarkable Mini Crown stent that I brought never did make it to prime time. He did, however, open the first live transmission of the conference by performing balloon angioplasty and stenting on a opera singer — while the patient belted out ‘O Sole Mio on the table(!).  This was my introduction to the Theater of TCT. Some years later, Colombo opened the conference by implanting perhaps a dozen drug eluting stents in one patient’s coronary arteries. In the opening live case of 2004, a percutaneous aortic valve procedure tragically devolved into urgent practice of CPR and defibrillator techniques. 2001 was one of the few years that I missed TCT; the conference was cut short on its second day by the events of September 11th. This year, for the first time ever, TCT left its home in DC, and came to my own back yard: The Moscone Center in San Francisco.

In recent years, the opening cases have been less flamboyantly Italian, and more conservatively Dutch or German. 2009 was no exception, but it was a highlight none the less. In the opening case from Seiburg, Germany, a CoreValve was successfully placed in a 92 year old patient with aortic stenosis. Recently purchased by Medtronic, the CoreValve device prominently features a  Nitinol frame — marking the first of many moments where Nitinol took center stage in Cardiology at TCT 2009. While Nitinol has been a headliner in peripheral vascular stenting, carotid stenting, vena cava filters, and guidewires for many years, this marked the first year where this unique material took center stage in matters of the heart.

Nitinol featured prominently in Wednesday’s Coronary Stent Design and Device Development session, which was so interesting that it prompted evacuation of the Moscone Center for an hour. Noted author Tom Duerig highlighted the unique properties of Nitinol in his Metals as Implantable Materials talk, followed by some spectacular data presented by Juan Granada demonstrating the performance of Prescient Medical‘s vProtect Luminal Shield, a Nitinol stent designed to stabilize vulnerable coronary lesions. The hits kept coming on Thursday, with over three hours dedicated to The Re-Emergence of Self-Expanding Coronary Stents, which included my contribution (on behalf of “Real Metallurgist” Alan Pelton), Important Stent Design and Delivery System Issues Make All the Difference for Coronary Stents. I joined an all-star cast including Renu Virmani, Barry Katzen, Rob Schwartz, and Stefan Verheye along with friends and fellow JJIS alumni Bob Burgermeister and Hikmat Hojeibane, all singing the praises of Nitinol as a solution for persistent challenges in coronary arterial disease. On this year that the center of the cardiovascular universe came to my home turf, Nitinol and NDC were stars at the heart of TCT Theater.

Weihenstephan: Älteste Braueri der Welt

Bravarian State BreweryFor some time, I’ve heard tales from my German colleagues of a mythical beer, brewed by monks for hundreds of years, atop a hill somewhere in Bravaria. A email exchange with Dieter, himself holidaying in the hills of the Black Forest, suggests that the beer is called Weihenstephan, and, in fact, it is brewed not far from München. Further research reveals that it is the “Oldest Brewery in the World”, now owned by the State of Bravaria, and is now associated with a technical university. So on my last day in Deutschland, I charted a course for the village of Freising, about a half hour north of my flat near the Hautbahnhof. I consulted the Internets to plan this excursion, and what I found was scarce, confusing, and/or in German. This, of course, contributed to the fun. But, I thought I would take the opportunity to tell the tale of my excursion. So, Interweb, here is my story…

Advance scouting: I found the Weihenstephan web site, which fortunately happens to provide an English version. The Guided Brewery Tour Page suggests that tours are offered at 10am on Monday, among various other times: Wunderbar! But then it also says “Guided Brewery Tour Only After Appointment”. What does this mean, I wondered, on Sunday night… I sent an email to the address listed, and received a well meaning but confusing response:

Dear Mr. Bonsignore,

Thank you for your inquiry. Unfortunately, it is not possible today in a tour with receives.

Yours sincerely,
Bayerische Staatsbrauerei, Weihenstephan

Huh? Well, since I received this reply while on the train to Freising, I wasn’t going to give up hope, and if nothing else, I would at least go see what the place looked like.

Getting to Freising: This little town is conveniently located at the end of an S-Bahn line, the S1 to be exact, which terminates at the Flughafen or Freising on its northern end. It also happens to be a stop on the main rail line heading from Munich to Prague, so I was able to grab Czech bound train on my way there, and Freising was the first stop. This cut the 45 minute S-Bahn trip down to about 25 minutes.

Getting to Weihenstephan: I arrived at about 9:15 am, and headed out of the station attempting to follow my Google Maps walking directions. Of course, I was immediately disoriented, but fortunately found that there were signs pointing to Weihenstephan, and just followed those: straight out the front door, left on a foot path along a canal, past a waterfall, right on another road, over a bridge, and then onto a steep foot path that climbs up the hill leading to the campus above. At the top of the hill, the path ends among some picturesque gardens that are part of the Technical University of Munich at Weihenstephan. The walk took about 20 or 25 minutes, so I was early for the 10am tour. Which was good, because it was completely unclear where the tour started, or if there was even a tour at all. I had to wander around quite a bit before finding the gift shop downhill on the other side of the campus. Here, I used hand gestures and semaphore flags to convey to the shopkeeper my confusion about the tour. She was able to call the office, confirm that there was a tour about to start, and sent me up the hill to meet the guide. Success!

WeihenstephanThe Tour: My group included an Italian family, two other guys, and me. I was the only one that didn’t understand German, but our guide was kind enough to translate the essential bits for me. I taught him that the English word for Gewürznelke is “Clove”, but I don’t think he believed me. He referred to carbon dioxide as CO-W, which I found too amusing to correct. He gave a great tour, even if I couldn’t understand 95% of it. The advertised 60-70 minute duration was actually closer to 3 hours, but regrettably didn’t include tastings (the only part I would have been able to completely understand). There is a restaurant on site, with an outdoor order-at-the-counter style Biergarten option, as well sit-down table service. I opted for the later, and had the ominous sounding but tasty “Pork Knuckle”, bretzels, potato dumpling, and kraut salat accompanied by the unfiltered Pils that’s only available on site, and the renowned Hefe Weiβeier before throwing in the towel. Despite reports to the contrary, they do offer 0.3L servings of some of the beers, but I opted for the 0.5L of each… And bought an assortment of six bottles to carry back downhill. Five of them were wrapped in diapers, packed in the luggage, and are now resting comfortably in my fridge, half a world from their origin, awaiting my liquid revisit of the adventure in the next few days.